Recording and controlling apparatus



April 19, 1949. R. B. COLT RECORDING AND CONTROLLING APPARATUS 4Sheets-Sheet 2 Filed Oct. 4, 1945 loithm .RM m 0 m6 Q\\ 1 1 Q RQHE mw kW R zoitkm Fwu 2 t. km kww R. B. COLT RECORDING AND CONTROLLINGAPPARATUS April 19, 1949.

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Filed Oct. 4, 1945 Patented Apr. 19, 1 949 RECORDING AND CONTROLLINGAPPARATUS Rutger B. Colt, Baltimore, Md., asslgnor to Bendix AviationCorporation, South Bend, Ind., a

corporation of Delaware Application October 4, 1945, Serial No. 620,211

Claims. 1

This invention relates to apparatus for recording and controllingvariations in a condition under observation and more particularly tosuch an apparatus in which means are provided for performing a controlfunction in response to the average of conditions existing at aplurality of test stations.

There are known in the art devices for recording changes in temperatureand humidity at a test location at a point remote from said testlocation. Such devices may be responsive either to changes in circuitresistance, circuit voltage or the frequency of the system voltage asdetermined by the condition responsive sensing element. Where it isdesired to continuously observe temperature and humidity characteristicsat several locations it is customary to, in effect, merely multiply theunits of the installation, providing parallel lines and duplicatetransmitting and recording apparatus. The problem of effecting a controloperation where the test locations are widely distributed throughout alarge structure or enclosure, served by a single conditioning unit isrendered dlfficult if it is desired to control average conditionsthroughout the enclosure. Energization of the control means by a singlecondition responsive sensing element maintains the controlledfactor atthe master test location substantially constant, while permitting thebalance of the test locations to execute wide excursions in thecondition which it is sought to control. Systems of this nature areparticularly sensitive to variations in the ambient and environmentalcircumstances which affect the controlling test location, as, forexample, a nearby opened window. Improved control may be guaranteed ifthe controlling action is made responsive to the average of theindications at each of the test locations.

Accordingly, it is a primary object of the invention to supply new andnovel means for effecting a control operation in response to the averageof conditions existing at a plurality of test stations.

Another object of the invention is to provide a new and novel apparatusfor periodically effecting a control operation in response to theaverage of conditions at a plurality of stations in which the lastposition of the control means is maintained until the receipt of newdata from the measurement averaging system.

A further object of the invention is to provide a new and novelmeasurement averaging system in which the indications for a plurality oftest stations are caused to successively actuate a summing device in anamount proportional to the individual outputs of the various teststaons.

Yet another object of the invention is to provide new and novelapparatus for printing and identifying a condition under measurement ata plurality of test stations.

Still another object of the invention is to provide new and novel meansfor determining the average of a plurality of observations.

Yet a further object of the invention is to provide new and novelcondition recording means in which the recordation may optionally takeplace continuously or at intervals spaced in time to permit a saving inthe recording medium used.

Still a further object of the invention is to provide new and novelmeans for recording and controlling in accordance with the average of aplurality of observations of conditions existing at a plurality of teststations.

The above mentioned objects and advantages of the invention may besubstantially accomplished in the illustrative apparatus configurationin which a plurality of test stations are sequen tially placed incontrol of a metering device developing a pulse at a time spaced fromthe establishment of such control an amount controlled by the conditionunder observation. An initiating pulse is provided by the sequentialswitching control to start operation of a summing device, with theoutput pulse of the metering apparatus serving to interrupt theoperation of said summing device, the summing operation continuingcumulatively throughout connection to a predetermined number of teststations, after which a control operation is effected and the summingapparatus reset or zeroized. Means are further provided whereby the lastposition of the controlling switch is retained until the receipt of anew averaged value of the measurements under observation.

Other objects and advantages of the invention will in part be disclosedand in part be obvious when the following specification is read inconjunction with the drawings in which:

Figure 1 illustrates the electrical structure of a test station,

Figure 2 is a schematic representation of the mechanical portion of thestructure,

Figure 3 is a schematic diagram of the electrical portion of theapparatus including the metering circuits, and

Figure 4 is a sequence diagram illustrating the interlocking operationof the various cam actuated switches.

'known in the art.

Figure 5 illustrates the printed record delivered by the completedevice.

Referring now to Figure 1 there is presented schmatically, theelectrical structure of the test stations 20, 22, 24, 26, 28, 30, 32 and34 of Figure 2. Each of said stations includes a temperature responsivemeasuring element and a humidity responsive measuring element, theinternal arrangements at the various stations being the same for allstations. The temperature responsive circuit includes a substantiallyfixed resistor 36 connected in series with a temperature responsiveresistor 38 which may be prepared from various metallic oxide or othermixtures well The series combination is connected between the terminals40 and 42 and the junction of the two resistors is connected to terminal44.

In operation, an electrical voltage is normally applied betweenterminals 40 and 42 and the variation in resistance of temperatureresponsive resistor 38 gives rise to a varying voltage, due topotentiometric action, between terminals 42 and 44, this varying voltagebeing related to the temperature obtaining at the particular teststation. These elements thus comprise the assembly respondingelectrically to changes in temperature.

For the purpose of determining the humidity existing at the teststation, there is incorporated a hair element 46 maintained undertension by the associated spring 48 and linked by arm 52 to a rotatableshaft bearing a conductive pointer 50. The end of pointer arm 50 ismovable in proximity to a resistor 54 electrically connected with thetest circuit energizing terminals 40 and 42, but not normally inmechanical engagement with resistor 54.

The clamping bar 56 is located over an extension of the arm 50 and isadapted to drive pointer 50 into engagement with resistor 54 in responseto energization of the relay operating coil 58. The mechanical link tothe clamp bar 56 is indicated at 60. The clamp bar 56 is preferablyconstructed of nonconductive material to avoid disturbance of theassociated electrical circuits. The pointer arm 50 is conductivelyconnected to terminal 62 and impresses between the terminals 42 and 62 avariable voltage controlled by the position of the pointer arm 50 on theresistor 54, which voltage is, therefore, indicative of the humidityexisting at the test station concerned. One end of the relay operatingcoil 58 is tied to the common terminal 42 while the other end of saidcoil 58 receives energy from the relay feed terminal 64.

The method of incorporation of the individual stations in the over-alltest scheme appears in Figure 2, illustrating a plurality of teststations 20, 22, 24, 26, 28, 30, 32 and 34 placed strategically aboutthe structure or space in which, say, the humidity is to be controlled.Each of the stations contains the same operating elements as detailed inconnection with Figure 1, and the same characters are employed indesignating the corresponding connecting terminals to each of the units,the station under discussion at any point in the text being indicated byits basic deslgnation number as; for example, station 20.

The various test stations are successively placed in control of meteringor measuring apparatus by the action of a selector assembly 66. Theselector assembly 66 includes, as shown, eight radially disposed andspaced leaf-spring switch pile-up assemblies, two of which 68 and I0,con- 4 nected respectively to stations 20 and 34, are shown in detail,the remaining switch pile-ups being merely indicated at I2, I4, I6, I8,and 82. The switches appear schematically shown in the drawing as viewedfrom their end. The switch assembly 68 is composed of four single-polesingle throw switches made up of four movable leafspring borne contacts84, 86, 88, and insulatingly linked by a tie element to move as amechanical unit. Fixed contacts 92, 94, 96, and 98 cooperaterespectively with the movable contacts 84, 86, 88 and 90, being inengagement with the associated contact when the innermost leaf spring 90is driven radially outward by one of the rollers IOI at the end of theswitch actuating arms I00, I02 and I84, which may be angularly spacedapproximately degrees. The outermost fixed contact 92 is linked to thetemperature terminal 44 of station 20 by the lead I06; the next inwardlysituated contact 54 is linked to the humidity terminal 62 of station 20by lead I08; the next inwardly spaced fixed contact 96 is conductivelyconnected with the test circuit energizing terminal 40 of station 20 bylead H0 and the innermost fixed contact 98 is attached to the relayenergizing terminal 64 of station 20 by the lead II2.

The fixed contacts corresponding radially in position to those in switchpile-up 68 whose detailed connection to station 20 has just beenrecited, are similarly connected to the remaining test stations, thedetail of such connections being omitted from the drawing, since theyare merely duplicates of those already shown, for the purpose ofsimplifying the presentation. Switch pile-up I2 serves station 22,switch pile-up I4 serves station 24, switch pile-up I6 serves station26, switch pile-up I8 serves station 28, switch pile-up 80 servesstation 30 and switch pile-up 82 serves station 32. I

The detail of the connection of the fixed contacts of switch pile-up I0to test station 34 is also shown to simplify the tracing of thecooperating interrelationship. In switch pile-up I0, the outer fixedcontact I I4 serves temperature contact 44 of station 34 through leadH6, fixed contact II8 serves-humidity contact 62 of station 34 throughlead I20, fixed contact I22 serves test circuit energizing contact 40 ofstation 34 through lead I24, and innermost fixed contact I26 servesrelay terminal 64 of station 34 through lead I28. The movable contactsI30, I32, I34 and I36 of switch pile-up I0 cooperate respectively withthe associated fixed contacts II4, I I8, I22 and I26 and are connectedto the corresponding movable contacts of the balance of the switchpile-up terminals through the inter-connecting cable representeddiagrammatically at I38. As seen, this cable inter-connects, in additionto the corresponding movable contacts on the intermediate switch pile-upassemblies, movable contacts I30, I32, I34 and I36 of the switch pi e-upI0 respectively to the movable contacts 84, 86, 88 and 90 of the switchpile-up 68.

In addition to the connection of the operating terminals of the variousstations thus far discussed, the common terminals 42 of each of saidstations are connected together and to the common line I39 whichestablishes a connection to terminal A for input to the meteringcircuits. The remainder of the connections necessary for the transfer ofoutput from the measuring elements to the metering apparatus passthrough the temperature lead I40, extending from the cable connected tomovable contact I30 to the upper contact I46 of a single-poledouble-throw cam actuated switch assembly I44; from the cable connectionat movable contact I32 to the lower fixed contact I42 of the single-poledoublethrow switch I44 through humidity lead I48, from the cableconnection at movable contact I84 through test circuit energizing leadI50 to the alternating current output terminal B of the meteringapparatus and from the cable connection at movable contact I36 throughthe relay energizing lead I52 to the direct current output terminal C ofthe metering apparatus. The spring leaf switch pile-up assemblies 66 to82 are arranged for successive actuation, as previously noted, by thepassage of the associated actuating arms I00,.I02 and I04 tipped withrollers lol. The actuating arm assembly is driven by the ratchet wheelI54, to which it is rigidly connected.

As shown in the drawing, ratchet wheel I54 is adapted for clockwiserotation through the action of the cooperating pawl I56 and ratchet stopI55. The pawl I56 is reciprocably driven through the rocker arm I56attached to the push rod I60 whose nose engages the station advance camI62. On the forward stroke of the push rod the pawl I56 is graduallyreturned from its extended position as the push rod I60 moves to theleft, extending the spring I64 having one end connected to the rockerarm I56 and the other attached to a fixed portion of the machine as atI66. When the push rod. I60 falls off the step on cam I62, the rockerarm I58 is snapped in a counter-clockwise direction under the influenceof stored energy in spring I64 driving the actuator arm assembly throughan angle substantially equal to the spacing angle of the switch pile-upassemblies.

The station advance cam I62 is located on a main drive shaft I 68 drivenby the main drive motor I through the reduction gearing unit I12. Asshown, the motor I10 is electrically powered, receiving energy from thepower bus lines I14 and I16, which may be linked to a commercial powerline circuit at I80 through the switch I18 In addition to the stationadvance cam, the shaft I68 may drive or carry a number of switchactuating cams, those shown being the tapper circuit disabling cam I82,the summation initiatin cam I84, the control latch relay energizing camI86, the summation reset cam I88 and the temperature/humidity selectorcam I90.

The single-pole double-throw switch I44, whose connection with themeasuring elements and selector switch 66 has been previously treated,is included in a group of three switches operated by thetemperature/humidity cam I90. When the cam follower is on the lowportion of cam I90 the movable arm I92 of single-pole single-throwswitch I44 engages contact I42 connecting the humidity responsive outputfrom the active test station through line I94 to the terminal D, whichis the measured signal input terminal of the voltage responsive'metering circuit later to be described. Included in the switch assemblydriven by temperature/humidity cam I90 are the singlepole double-throwsweep potentiometer selector switch I96 and the single-pole double-throwtapper circuit selector switch I98.

The central contact arm 200 of sweep potentiometer selector switch I96is alternatively engageable with an associated upper contact 202connected to the rotatable arm 204 of the temperature sweeppotentiometer 206, and with lower contact 208 connected to the movablearm 2| 0 of the humidity sweep potentiometer 2I2. The

temperature sweep potentiometer 206 has the extremities of the activeresistance winding 2 connected to the terminals E and F of the mainelectrical unit from which it receives an adjustable potential through acircuit of adjustable internal impedance. Similarly, the extremities ofthe active resistance element 2I6 of the humidity sweep potentiometer2|2 are connected to the terminals G and H of the main electrical unitto which there may be applied an independently variable voltage from asource of independently variable impedance.

The temperature sweep arm 204 and the humid ity sweep arm 2I0 are drivenby a shaft 2| 8 rotating at such a rate that it makes two completerevolutions per revolution of the main drive shaft I68. For the sake ofillustration this is shown to be accomplished by the interposition of a2:1 step-up transmission gearing unit 2 I5 linking the main drive shaftI68 and the sweep shaft 2I8. In addition to driving the sweeppotentiometer arms, shaft 2I8 also carries with it a printing wheel 220provided with two sets of characters 222 and 224, the former of whichcorresponds to temperature indications while the latter corresponds tothe humidity conditions to be recorded. The printer wheel 220 isindicated as forming part of a unit assembly including two other printerwheels, one of which, the station printer wheel 226, is connected withthe intermittently indexed ratchet wheel I54 through the mechanicallinkage indicated as 228. The remaining printer wheel 230 bearscharacters identifying the time of a given observation, and is drivenfrom the timer motor 232 through the timer shaft 234, also carrying theprinter control cam 236. The timer motor 232, like the rest of themotive power in the assembly, is fed with alternating current from themain supply buses I14 and I16.

From the description and the schematic portrayal of the printer wheelassembly, it is apparent that wheels 220, 226 and 230 are revolvableindependently of one another. Printer wheel 226 and character set 222 ofprinter wheel 22!! are located adjacent to tapper bar 238, mounted on arocker arm 240 adapted for actuation in response to energization of anassociated relay coil 242. The time printer wheel 230 and character set224 of printer wheel 220 are in cooperative relationship with a secondtapper bar 244, mounted on rocker arm 246 adapted for actuation by theassociated relay coil 248. One end of each of the tapper operating relaycoils 242 and 248 is connected together and to the main power bus I14,the free end of the temperature tapper coil 242 bein connected to theupper contact 250 of the tapper circuit selector switch I98, while thefree end of the humidity tapper coil 248 is connected to the lowerterminal 252 of said tapper circuit selector switch I98. The movablecentral contact 254 of tapper selector switch I98 is fed with energyfrom the main power bus I 16 through line 256, the fixed contact 258 oftapper control relay 260, the movable contact 262 of tapper controlrelay 260, line 264, the normally disengaged movable contact 266 andfixed contact 268, comprising the printer control switch 212, and theline 210. The automatic printer control switch 212 is shunted by themanually operable single-pole single-throw switch 214. When switch 214is open and the printer control cam 236 is revolving at a normal speedof once every 24 hours no printing operation will take place, until theelevated portion of the cam 236, which may be designed to each occupy anare corresponding to fifteen minutes of revolution, pass under the camfollower, at which time the switch 212 is closed and the tapper relaycircuits will be energized upon each closure of the contacts of thetapper control relay 260, in response to impulses arriving from the mainelectrical unit through terminals J and K and leads 259 and 26I.Selection of the tapper bar to be energized is automatically made by theoperation of the tapper circuit selector switch I98 to print datacorresponding to the instantaneous condition under observation. Theactual printing takes place on the conventional strip chart 216 locatedadjacent the tapper bar, through the action of an adjacent inked band orcarbon ribbon 218 situated between the strip chart and the characterbearing printing wheels. The chart feed is conveniently of the solenoidor ratchet advance type, in which the strip chart is advanced once foreach tapper bar operation. When it is desired to effect a continuousprintin operation the switch 214 may be closed to efiectively remove theprinter control switch 212 from the circuit.

When the low portion of the temperature/humidity cam I90 is under thecam follower, humidity measurements are made, and when the high portionthereof passes under the cam follower temperature measurements are made.The summation initiating cam I84, rotating synchronously with thetemperature/humidity cam I90, is provided with an elevated portion,called the cam rise, starting somewhat subsequent to the low portion ofcam I90 and occupying a sector of perhaps degrees. This cam operates anassociated summation initiating switch assembly 280 which is closed whenthe cam follower is on the rise of cam I84, and open at all other times.The summation initiating switch assembly 280 is connected in series withthe summation latchin relay winding 282 across the main power bus lineI14, I16. When switch 280 closes to energize the relay coil 282, themovable contact 284 of the summation latch relay 286 is pulled againstthe adjacent fixed contact 288, while at the same time its free endslips into the latch-in notch of the latch bar 290 urged upward by anattached spring 292. Contacts 284, 288 therefore remain in engagementeven after the removal of voltage from the relay latch-in coil 282.Closure of contacts 284, 288 completes the power input circuit forsummation motor 294 to the main power supply bus line I14 through lead296 and to the main power supply bus line I16 through lead 298, contacts284, 288 and lead 300. The motor 294 when so energized turns in aclockwise direction, driving a control cam 302 through the shaft 304,also carrying a brake wheel 306. When so operating, the spring 308 isextended as the cord 3I0 is wound on a drum 3I2 which is an integralpart of the brake wheel 306. In so driving the brake wheel 306, thesummation motor 294 also overcomes the resistance of a brake shoe 3I4maintained in frictional engagement with the periphery of the brakewheel 306 by a spring 3I6. When the tapper control relay 260 isenergized from the main electrical unit to close contacts 258, 262, thelead 3I8 extending from contact 282 to latch release coil 320, and lead322 extending from the other terminal of latch release coil 320 to thepower buses I14, I16 serve to energize the latch release coil 320pulling down the latch bar 290, releasing the movable contact 284 whichthereupon opens the electrical circuit to the summation motor 294. Thedelay between the initiation of the operation of the summation motor 294and its interruption, is determined by the value of the humidityexisting at the test location, since the actuation of the tapper controlrelay 260 occurs at a time delayed over initiation of the summationmotor operation by the length of time taken for the movable arm MD ofthe humidity sweep potentiometer 2I2 to reach a point developing avoltage proportional, in this case, equal, to the output of the humiditysensing element. Upon the opening of the summation control switch 284,288 and the interruption of the power supply to the summation motor 294,return of the control cam 302 to its initial position is preventedthrough the action of the brake shoe 3l4 resting on the brake disc 306affixed to summation shaft 304. Each time that a newstation is placed inconnection with the metering circuit this sequence of operation repeats.After the summation of the indications from, in the illustrated example,eight test stations, the summing mechanism is cleared or reset to zeroby the apparatus next to be described.

In addition to the selector switch actuator arm the ratchet wheel I54also drives the recycle cam disc I51, having on its periphery threeprojections I59. Simultaneously with the actuation of switch pile-upassembly 10, the recycle cam projection I59 passes under the follower ofthe normally open cam switch I6I, having one terminal thereof connectedto the power bus I14, through lead I63 and the other terminal connectedto one pole of the control relay energizing switch 324 through lead 325,and to one pole of summation reset switch 326. The summation reset camI88 is provided with a cam rise beginning somewhat subsequent to thestart of the high portion of the temperature/humidity cam I90 to preventoperation of the switch 326 prior to the completion of the humiditymeasuring operation. The closure of the control relay energizing switch324 also occurs after the start of the high portion of thetemperature/humidity cam I90, but the switch 324 opens prior to theclosure of the summation reset switch 326. The switch 326 may remainclosed for substantially 60 degrees of rotation of the main drive shaftI68. When the switches I6I and 326 are simultaneously closed, the lead328 connected to one terminal of the summation reset relay coil 330having its other terminal connected to the main power bus I16, serves toimpress on said summation reset relay coil 330 energy from line I14through recycle switch I6I and reset switch 326. The relay coil 330 isso situated with respect to the arm bearing brake shoe 3I4, as to drawsame back against the tension of spring 3I6, releasing the brake disc306 from restraint and permitting it to rotate counter-clockwise underthe influence of restoring spring 308 acting on cord 3I0 until the stoppin 333 strikes the reference abutment 335, which may be affixed to theframe of the apparatus.

Somewhat prior to this reset operation, however, the cam rise on thecontrol latch relay energizing cam I86 closes the control relayenergizing switch 324, whose movable pole is connected through lead 332to one terminal of the control latch-in relay coil 334 and one terminalof the control latch release relay coil 336. The free terminal of thecontrol latch-in relay winding 334 is connected with the upper fixedterminal 338 of the single-pole double-throw summation cam switch 340,and the free end of control latch release relay winding 336 is connectedwith the lower fixed contact 342 of the summation cam switch 340. Solong as the cam follower of the switch 340 rotates on the lower dwell ofthe summation cam 302 the movable member 344 of the summation cam switch340 is in engagement with the lower contact 342 and thus connected tothe latch release relay winding 336.

As the summation cam 302 rotates clock-wise the intermediate dwellportion thereof passes under the cam follower, moving the central switchelement 344 to a position clearing both the asosciated contacts, wherebyit is connected with neither of the control latch relay coils.Continuing rotation of the summation cam 302 brings the high dwell underthe cam follower of 340 driving central contact 344 into engagement withupper contact 338 to connect it with the control latch-in relay winding334. It is to be noted that the energy supplied through main power busI14 to the control latch relay circuits passes through lead I63 and therecycle switch IBI and lead 325 only when the recycle switch I6I andcontrol relay energizing switch 324 are simultaneously closed, as at theend of the completion of an averaging sequence. Then, and only then,power bus energy appears-at lead 332 and a circuit through one of thecontrol latch relay coils is completed in accordance with the positionof summation cam switch 340. If on the low dwell portion of the cam, asillustrated in the drawing, the latch release relay coil 336 isconnected to power bus I16 through contacts 342, 344 drawing up thelatch bar 346 against the action of tension spring 348 permitting themovable contact 350 to move out of engagement with the fixed contact352. In the event the cam follower is on the high dwell, the latch-inrelay coil 334 is connected to the power bus I16 through contacts 338and 344 and pulls movable contact 350 into engagement with the contact352, while at the same time the latch bar 346 slips down over the freeend of contact 350, maintaining same in engagement until actuation ofthe control latch release relay 336. Closure of contacts 350, 352establishes a connection from line I16 through lead 354 and lead 356 toa dehumidifier motor 358 whose remaining terminal is directly connectedto the power bus I14. The excessive humidity is then corrected.

By the time the reset switch 326 closes, the control energizing switch324 has already reopened, for it has a short closure period so that theresetting of the summing mechanism does not disturb the position of thecontrol latch relay 331. When the control latch relay energizing switch324 closes subsequently, the ratchet wheel I54 will have been indexedone position forward to bring the projection I59 on the recycle cam I51out from under the follower of recycle switch I6I to open same andmaintain the control relay energizing circuit non-operative until thecompletion of another averaging operation. It is to be noted that thelast selected position of the circuit controlling contacts 350, 352 ismaintained so long as the follower of summation switch 340 remains onthe intermediate dwell portion of the summation cam 302 and that, byvarying the length of the intermediate dwell portion the operatingdifferential may be correspondingly controlled.

i The operating sequence of the various cam control switches based on aminute averaging cycle is clearly portrayed in Figure 4, wherein thegraph 360 illustrates the manner and duration of operation of theswitches under control of the temperature/humidity cam I90. 362 isindicative of the operating cycle of the summa is, however, aspreviously described, wired in se- Ell ries with the recycle switch- I6Iclosing only on the completion of test at eight stations, this beingshown in the diagram at 366. After the control relay energizing switch324 is closed and opened after actuating the control latch relay 331,the summation reset switch 326 is closed under the influence of cam I88in the cycle shown at 368.

The operation of the station advance cam I62 appears at 310, each of thediscontinuities of the saw tooth characteristic corresponding to an ad-"vance of the switch actuator arms in the selector assembly 66 from oneswitch pile-up to the next. The significance of the switch sequencediagram 312, which illustrates the action of the tapper disabling switch314 under the influence of cam I82, will be more thoroughly discussedafter an analysis of the circuit of the main electrical unit.

Reference for the structure of the electrical unit is now made to Figure3 in which the electrical connections are shown brought out to terminalsidentified by letters, the terminals in Figure 2 and Figure 3 bearingthe same identifying letter being connected in normal operation of theapparatus. The direct current output terminal C supplying energy for thehumidity pointer clamp relay 58 at the test stations is fed withrectified energy derived from the heater circuit of the full waverectifier 315 having its anodes connected ,to either end of' the centertapped secondary winding 316 of the transformer 318.

The center tap of the winding 316 is grounded to supply a negativereturn. Heater energy for the rectifier 315 is supplied from secondary380 from one terminal of which the direct current output passes throughfilter chokes 382 and 384 to the output terminal C. The possiblytroublesome hum component is removed from the output existing atterminal C by the connection of filter capacitor 386 to ground from thejunction of chokes 382 and 384 and the connection 01' output filtercapacitor 388 between terminal C and ground. As is evident from thedescription and schematic, this comprises the usual choke input, fullwave rectifier characterized by rather good regulation between no loadand full load. The power transformer 318 is also provided with anotherset of windings for supplying anode circuit energy to a number of vacuumtubes incorporated in the main electrical unit. This anode supplyincludes another full wave rectifier tube 390, having its anodesconnected to either end of the center tapped secondary winding 392 andderiving its heater circuit energy from the secondary winding 394.Grounding the center tap of the secondary 392 provides a negative returnto the rectifier circuit, and the positive output slstor 404 and the twocold cathode gas discharge voltage regulating devices 406, 408 toground. There thus appears between the anode terminal 11 of the gasdischarge regulator 486 and ground a voltage substantially independentof the alternating potential existing in secondary winding 392 and ofreasonable variations in the load current drawn from said circuit.

The power transformer 318 also has a winding M8 to provide heater powerfor the remaining tubes in the apparatus. These heaters have beenomitted in the drawing for the sake of clarity since their use andcircuits for energizing same are well known in the art. The energy forthe secondary loads of power transformer 318 is derived from the primary4I2 connected to the main power bus I14, I16 through the terminals M andN.

The measured signal input to the electrical unit arrives from theassembly of Figure 2 at terminal D connected to contact 4l4 of thecalibrazion switch 6. When the rotatable arm M8 is in engagement withsaid contact 4 I 4, the measured signal passes on through the line 428to one terminal of the primary 422 of measured signal input transformer424. The remaining terminal of primary 422 is connected to ground asshown. The sweep signal input from the potentiometer circuits isimpressed on terminal S and thence via lead 426 on one terminal of theprimary 428 of the sweep signal input transformer 438 whose otherprimary terminal is grounded. Each of the transformers 424, 438 isprovided with a secondary winding 432, 434, respectively, one each ofthe terminals of said secondary windings being connected together. Thefree terminal of winding 432 is connected through diode rectifier 436 toa load resistor 438 shunted by a filter capacitor 448 while the freeterminal of secondary 434 is connected through the sweep signalrectifying diode 442 to the load resistor 444 shunted by filtercapacitor 446. The remaining terminals of load resistors 438, 434 andfilter capacitors 448, 446 are joined together and connected to thecommon terminal of secondary winding 432, 434. There is no ground inthis portion of the circuit.

The end of resistor 438 attached to the cathode of diode 436 isconnected to the control grid 448 of the triode valve 458 having itsanode 452 connected to the D. C. winding 454 of the saturable corereactor 456. Similarly, the end of resistor 444 attached to diode 442.is connected to the control grid 458 of the triode thermionic valve 468whose anode 462 is connected to one terminal of the D. C. controlwinding 464 of a saturable core reactor 466. The direct current pathbetween the grids and cathodes of the triode valves is completed by theconnection of resistors 468 and 418 in series between the control grids448 and 458, the junction point of said resistors being connected toground. The cathode 412 of triode valve 458 and cathode 414 of triodethermionic valve 468 are connected together and to one terminal of thebias resistor 416, whose other termi nal is grounded. Anode excitationfor the thermionic tubes 458 and 468 is supplied by the connection ofone terminal each of the D. C. control windings 454 and 464, to eitherend of a resistor 418 having a tap 488 movable thereover connected tothe anode terminal of regulator 486 through the lead 482. Unbalance inthe characteristics of the tubes and the saturable core reactors iscorrected by adjusting the tap 488 to balance the impedance of thesaturable core alternating current windings, with no signal input atterminals S and D.

The pair of tubes 458 and 468 constitute a differential voltmeter inwhich the anode current of each tube is caused to vary symmetricallyfrom its quiescent value in response to unbalance between the measuredsignal input at terminal D. The saturable core reactor 456 is providedwith two alternating windings 484 and 486, connected in series phaseopposition to minimize alternating current flux flowing in the corestructure. Likewise the reactor assembly 466 includes two alternatingcurrent windings 488 and 498, also connected in series to minimize thealternating flux resulting from the presence of A. C. in the controlwindings. The free terminal of A. C. winding 484 is connected with oneterminal of a center-tapped secondary 492, of a motor supply transformer494, and the other end terminal of secondary 492 is connected with thefree end of A. C. winding 498. The transformer 494 is energized by theprimary 5l2 having its terminals connected across the main power buslines 589 and 5| I fed from terminals M and N.

The free terminals of windings 486 and 488 are connected together, andto one terminal of the field winding 496 of the drag-cup motor indicatedat 498. The other field winding 588 included in the drag-cup motor isconnected to the main power supply bus lines 589 and 5 through a phasingcapacitor 582. The drag-cup 584 of the motor 498 has afiixed thereto aconductive arm 586, adapted to move between the fixed insulatingabutment 588 and a contact 5l8. The contact 5l8 is connected with theanode of the gas discharge regulator tube 486 through anode bus lead5I2. The windings 496 and 588 are disposed in space quadrature adjacentthe drag-cup 584, and as is well known, when a cur-' rent passes throughone of the windings having a quadrature component with respect to thecurrent passing through the other of said windings, the rotatingmagnetic field carries the drag-cup 584 with it, due to interaction ofeddy currents appearing in the drag-cup 584 and said rotating magneticfield.

So long as the impedance presented by saturable core reactors 456 and466 is equal, no current flows in the central leg formed by theconnection of field winding 496 between the common terminal of the A. C.windings thereof and the cententap of transformer 492. As soon as thereis an unbalance in the impedance of the saturable core reactors 456 and466, an equalizing current flows through field winding 496, the phase ofthis current, with respect to the voltage across winding 492, varying inaccordance with the sense of impedance unbalance. Hence, with animpedance unbalance of one sense, the drag-cup 584 rotatescounter-clockwise driving the pointer 586 into contact with the abutment588, and when the sense of the impedance unbalance reverses the drag-cup584 rotates clockwise, bringingarm 586 into engagement with the contact58 I. The point at which this change in the tendency'of drag-cup 584 torotate occurs when the impedance of the two saturable core rotators 456and 466 passes through the balance point.

The arm 586 is connected through lead 5 to the series connectedresistors 5i6 and 5l8. One terminal of resistor 5l8 is grounded and theungrounded terminal of said resistor 5l8 is connected through couplingcapacitor 528 to the grid 522 of a gas tetrode 524, whose anode 526 isconnected to the anode supply bus 5l2 through a limiting resistor 528.The grid leak 538 is connected between grid 522 and ground and thecathode 532 is connected with the shield grid 534 and to the tapperimpulse output terminal J.

The return circuit from the operating coil of the tapper control relay266 to the tapper impulse circuits is completed through terminal K andresistor 542 to lead 536. TerminalL is connected directly through lead536 to the ungrounded terminal of resistor I38. situated in a voltagedivider including resistor 546 connected between anode supply bus I2 andthe ungrounded terminal of resistor 538. The tapper impulse energy isderived from the storage capacitor 535 connected between anode 526 andthe lead 536.

The voltage drop across resistor 538 makes the cathode 532 positive withrespect to ground and hence provides operating bias potential betweencathode 532 and control grid 522 which is grounded through resistor 530.The terminals K an L, in Figures 2 and 3, are connected through leads26I and 263 with the normally closed tapper circuit disabling switch 314of Figure 2. The switch 314 is opened whenever a rise of the tapperdisabling cam I82 passes under the follower of the tapper disablingswitch 314. When closed, the switch 314 short circuits terminals K and Lto remove the surge limiting resistor 542 from the circuit including thereservoir capacitor 535, the tapper control relay coil 266 and theanode-cathode path of the gas tetrode 524. This condition obtains duringthe active portion of the measuring cycle. During the retrace of thesweep voltage, which is to say during the transit time of the arms 204and 2"], between the open ends of their associated resistance windings,the switch 314 is maintained in open circuit position thereby insertingsurge limiting resistor 542 to prevent actuation of tapper control relaycoil 260, and the tapper bars 236 and 242 under its control.

In the course of normal operation, when the arm 506 engages contact 5H)2. positive pulse is transmitted through capacitor 520 to the controlgrid 522 of the gas discharge tetrode 524. This tube will usually havebeen in the quiescent state for some time previously, permitting thecapacitor 535 to charge from the anode supply bus 5I2 through thelimiting resistor 528. When a positive pulse is applied to the grid 522at the same time that the anode 526 is maintained positive by capacitor535, ionization is initiated within the tube 524, permitting currentconduction there-through with relatively low voltage drop, so that thecapacitor 535 may be regarded as instantaneously connected across theoperating winding of tapper control relay 260, when the switch 314 is inthe closed circuit condition shunting out surge limiting resistor 542.In the event that switch 314 is opened, the peak surge current which canbe developed through resistor 542 is so reduced in magnitude that it isunable to overcome the opposing spring force of relay 266, which ishence prevented from operating and no mark is impressed on theassociated strip chart, although the reactors 456 and 466 may havereturned through the balance point. It is thus apparent that the tube524, reservoir capacitor 535, and motor 498 driving contact arm 586comprise a current surge generator delivering current surges capable ofoperating tapper control relay 260 whenever the surge limiting resistor542 is shunted out of the capacitor discharge circuit.

The time sequence diagram of Figure 4 clearly illustrates the operationof the tapper disabling switch 314 to insert surge limiting resistor 542during the switching interval between the two types of testing operationand an overlapping period on either side thereof. The switch open [illdwell of cam I82 may preferably occupy a time interval substantiallyequal to or somewhat greater than that required for the passage of thesweep potentiometer arms through the inoperative azimuthal portion ofrotation represented by the angle subtended by the terminal points ofthe associated resistance windings. The presence of two cam riseintervals on the tapper circuit disabling cam is necessitated by the 2:1speed ratio between shafts I68 and 2I8.

The alternating potential required for the energization of the measuringelements of the various test stations is derived from the test circuitenergizing secondary 544 of transformer 546, whose primary 548 isconnected with the A. C. busses 569 and 5I I, through leads 556 and 552.One terminal of Winding 544 is connected to the ground and to the commonterminal A, while the other terminal thereof is connected with A. C.output terminal B and, through lead 554. with the voltage dividerresistance networks 556, 558 and 560, 562 whose other terminals areconnected to ground. The intermediate point on divider 556, 558 isconnected with the contact 4 I 5 of calibration switch 4 I 6, and theintermediate point on voltage divider 560, 562 is connected with contact4I1. Movement of the contact arm MS of calibration switch 4I6 thusoffers means for impressing predetermined voltages on the primary 422 ofthe measured signal input transformer 424 for calibration of theapparatus in a manner subsequently to be outlined.

In addition, transformer 546 carries a sweep signal secondary winding564, having an inter mediate tap 568 brought out. One end of sweepsignal secondary 564 is connected to ground and a resistor 566 isconnected between this grounded secondary terminal and tap 568. Theadjustable tap 510 is movable over resistor 566, and connected withterminal F to provide for adjustment of the voltage applied to thetemperature sweep potentiometer 206. Also movable over resistor 566 is atap 512 connected with terminal H and V providing for an adjustment ofthe voltage applied to the humidity sweep potentiometer. The other endof the temperature sweep potentiometer circuit returns through terminalE, the line 514 andthe adjustable resistor 516 to the ungrounded endterminal of sweep signal secondary winding 564. The inclusion ofadjustable resistor 516 in the sweep potential energizing circuit,permits regulation of the effective source impedance. The circuit fromthe humidity sweep potentiometer 2l2 returns to terminal G, through lead518 and adjustable resistor 580 to the ungrounded end terminal of sweepsecondary winding 564, which arrangement also provides for adjusting theimpedance of the source of excitation voltage.

With the foregoing in mind, the operation of the apparatus is readilyunderstood. With the closure of switch I18, the timer motor 232 and maindrive motor I10 are energized. It will be assumed that the stationselector is in the position shown at Figure 2. The clamp relay coil 58of station 20 is energized through lead II2, cable I38 and lead I52 toengage the humidity pointer with its associated resistor strip 54. Thisimpresses on theterminal 62 a voltage indicative of the humidity whichis transmitted to the temperature/humidity measuring signal selectorswitch I44 with the apparatus in the condition of Figure 2. This voltagepasses on to the measured signal input terminal D of the measuringapparatus. So long as the low dwell of cam I90 is under the camfollower, this connection is maintained. The A. C. energy for excitingthe measuring elements at station 20 passes from terminal B through thelead I50, cable I38 and lead III) to terminal 40. As the shaft I68continues to rotate the summation initiation switch 280 is closed tolatch-in the summation relay 286 and set the summing motor 294 inmotion. With the continuing rotation of shaft I68, initiating switch 280reopens, but the operation of summation motor 294 continues because ofthe latch-in action of relay 286.

Initially, a high sweep signal voltage is derived from the humiditymeasuring potentiometer 2 I2, and impressed on sweep signal input signalterminal S, causing an unbalance in the output of the diodes 436 and442, up-setting the impedance balance of the saturable core reactors456, 466 because of the different anode currents flowing through thethermionic valves 450 and 460. The poling of the motor and controlcircuit connections is such that, for this condition, the arm 506connected to the drag-cup motor 498 is forced against the abutment 508.As the arm of the humidity sweep potentiometer 2I0 continues to rotate,the voltage applied to terminal S through the temperature/humidity sweepselector switch I96, passes through a value equal to the measured signalinput at terminal D. At this time, the impedance unbalance betweensaturable core reactor 456 and 466 is reversed, causing a reversal intorque developed by the drag-cup motor 498 to drive the contact arm 506into engagement with the contact 5I0. This impresses a positive pulse onthe control grid 522 of the tetrode gas discharge tube 524, ionizing thegas within the tube to discharge the capacitor 535 through the tappercontrol relay operating coil 260. This closes the contacts 258, 262 oftapper control relay 260 to energize the latch release coil 320 withinthe summation control latch relay 286, halting the operation ofsummation motor 294. The shaft 304 and summation control cam 302 aremaintained in their position at this moment by the brake 3I4. When theprinting control cam 236 closes the print control switch 212, which itdoes for a minute period at 12 hour intervals in the example shown, theclosure of contacts 258 and 262 also energizes the humidity tapper coil248 through the temperature/humidity tapper selector switch I98controlled by cam I90. Since the position of the printer wheel 220 islinked with the output voltage of the sweep potentiometer 2I2, thecharacter printed is determined by the humidity control voltage atterminal 62 of station 20, for the tapping operation takes place, in thecircuit shown,

when the voltage developed by the potentiometer 2 I 2, and the voltageat terminal 62 are equal. The same principle may be utilized withoutestablishment of equality between the voltages, if the turns ratio ofthe measured signal input transformer 424 and the sweep signal inputtransformer 430 are made unequal. When the arm 2I0 of the sweeppotentiometer 2I2 reaches the end of the resistance winding 2I6, orpreferably slightly earlier, the tapper disabling switch 314 is openedby cam I82 to insert the surge limiting resistor 542, in series with theenergizinz circuit for the operating coil of tapper control relay 260,whose operating circuit then comprises capacitor 535, tube 524, terminalJ, relay 260, terminal K and resistor 542. This prevents possibleprinting during the period when the unbalance sense of the measuredsignal and the sweep signal is restored to that prevailing at thebeginning of the measuring cycle. Since this restoration is accompaniedby a passage of the relative impedance values of the alternating currentwindings of saturable core reactors 456 and 466, through the point ofbalance, reversing the torque developed by drag-cup motor 458, shouldthe conductive arm 506 bounce against the abutment 508 at this time, thecontact 580 might accidentally be touched to cause an undesired printingoperation. This, however, is avoided by disabling the printer circuitduring the retrace interval. The printing wheel 230, provided withcharacters corresponding to time, is propelled by timer motor 232, andimprints on the chart 216 the time corresponding to each humiditymeasurement in response to the same movement of tapper bar 244.

During the period when station 20 is the active station, that is, thestation in control of the metering apparatus of Figure 3, the recycleswitch I6I is open, preventing energization of associated apparatus bythe closure of control relay energizing switch 324 or summation resetswitch 326. With the continuing rotation of shaft I68, the high dwell ofcam I passes under its associated cam follower, actuating switches I44,I96 and I98 to connect the temperature voltage output terminal 44 oftest station 20 to the measured signal input terminal D, the arm 204 ofthe temperature sweep potentiometer 206 to the sweep signal terminal S,and the temperature tapper coil 242, with the tapper control contact 262of the relay 260.

Again the sweep signal output voltage is varied and passes through avalue equal to the temperature output voltage to actuate the tappercontrol relay 260 and, this time, tapper bar 238 prints from thecharacter set 222 of wheel 220 and the characters on printing wheel226,corresponding to station under test, in this case station 20. Thetwo character sets 222 and, 224 rotate together,

being part of the same printing wheel, and the potentiometer arms 204and 2I0 rotate synchronously therewith, the whole assembly being drivenfrom the cam shaft 2I8. It is thus seen that during the second half ofthe observation cycle, the temperature and the number of the station towhich the humidity and temperature test appertain is imprinted.

The summation cam 302 is now maintained in a position corresponding tothe first humidity measurement with the continuing rotation of shaftI66. The push rod I60 falls ofi the cam step indexing the switchactuator arm I00 clockwise through approximately 15 degrees, permittingthe switches in pile-up 68 to return to their normal opening positionwhile closing those in pile-up 12. The cycles previously described arenow completed with test station 22 in control of the metering apparatusto print the temperature, humidity, station number, and time ofobservation on the strip 216 as shown in Fig. 5, which has meanwhilebeen indexed one step forward during the transfer of active stations, byconventional mechanism, not here described or shown.

After completion of the observations for station 22, the same process issuccessively repeated for stations 24, 26, 28, 30, 32 and 34. When theactuator arm I00 closes the switch in pile-up 10, connected with teststation 34, the recycle switch I6I is closed so that, after completionof the humidity measuring operation, when the cam rise on controlenergizing cam I86 closes switch 324, energy is supplied to the controllatch relay l7 331 which assumes one position or the other dependingupon the degree of rotation of the summation cam 302, which has by nowbeen rotated a total amount proportional to the sum of the humidityindications at the various test stations which have been sequentiallyplaced in control of the metering apparatus of Figure 3. The totalrotation of the cam 302 is thus proportional to the average of theindications at the eight test stations, and the actuation of the controllatch relay 337 is hence determined by the average of these values. Asshaft I68 continues to rotate the switch 324 opens, and shortlythereafter reset switch 326 closes under the influence of cam I88 toretract the brake shoe 3, resetting the summation shaft 304 to itsreference position. The condition of the control latch relay 331 so setin is retained until the application of a different stimulus resultingfrom a subsequent averaging operation, and the operation ornon-operation of condition correcting motor or load 358 is so determinedat minute intervals.

The averaging and efiectuation of control is carried out continuouslywhatever the condition 01' the printer control switches 212 and 214.When e either one of these switches is closed, the same impulse whichunlatches the summation control I latching relay 286 also energizes thetapper bar corresponding to temperature or humidity, as the case may be.station indicating and time printing wheels, there are shown oppositeeach set of observations the number of the station to which theobservations correspond and the time at which they were made.

The use of two sweep signal potentiometers linked to a signal printingdevice from the temperature/humidity indications is explained by thedesirability of providing for independent circuit compensation to matchvariations in the temperature/humidity responsive apparatus to thedistribution of the fixed character sets on the printing wheels. Anincrease in the source impedance feeding the potentiometers increasesthe rotation corresponding to a given tempera-- ture/humiditydifferential thus spreading the scale and vice versa. A change in thepotential of the low voltage end with respect to ground offers the meansfor changing the point in rotation at which a predetermined outputvoltage is delivered through the sweep signal potentiometer thusproviding for lateral scale adjustment Without material change in thescale modulus.

When the apparatus is first installed, the series resistance controls516 and 580, control 510 and 512, are employed to adjust the circuitimpedance and voltage, to insure the desired voltage vs. rotationcharacteristic and hence the desired scale distribution of the printingelements. This is performed initially by first placing the arm 8 ofcalibration switch on contact "5 on which may provide a voltagecorresponding subsequently to a full test rotation of the sweeppotentiometer and adjusting the applicable voltage controlling tap 510or 512 to print the character properly associated with such voltage.Thereafter. the arm 8 may be placed on contact ll! delivering a voltagecorresponding to that supplied within the first few degrees ofrevolution of the sweep signal potentiometer and adjusting the propercontrol 586 or 580 to cause the printing of the proper character fromthis position. With a sufiiciently low value of resistor 5", thesecalibrationoperationsmay be substantially freed of any interlockingefiect.

Due to the juxtaposition of the and the voltage The invention may beembodied in other speciflc forms without departing from the spirit oressential characteristics thereof. The present embodiments are thereforeto be considered in all respects as illustrative and not restrictive,the scope of the invention being indicated by the appended claims ratherthan by the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced thereby.

What is claimed is:

1. In a system for controlling a condition in response to the average ofa plurality of observations, a plurality of measuring means derivingvariations in said condition, means deriving the sum of the indicationsof said measuring means in a summing sequence including a singleindication only from each of said measuring means, and circuitcontrolling means actuated by said sum responsive means.

2. In a system for controlling a condition in response to the average ofa plurality of observations, a plurality oi measuring means responsiveto variations in said condition, means successively and additivelyresponsive to the indications of said measuring means taken in apredetermined sequence, and circuit controlling means actuated by saidadditively responsive means.

3. In a system for controlling a condition in response to the average ora plurality of observations, a plurality of measuring means responsiveto variations in said condition, means successively and additivelyresponsive in a predetermined sequence including a single indicationonly from each of said measuring means to the indications of saidmeasuring means,circuit controllingmeans actuated by said additivelyresponsive means and means for periodically restoring said additivelyresponsive means to a predetermined position.

4. In a system for controlling a condition in response to the average ofa plurality of observations, a plurality of measuring means responsiveto variations in said condition, means successively and additivelyresponsive to the indications of said measuring means, circuitcontrolling means actuated by said additively responsive means, andmeans for energizing said circuit controlling means after the successiveapplication of the indications of a predetermined number of saidmeasuring means to said additively responsive means and de-energizingsaid circuit controlling means at all other times.

5. In a system for averaging a plurality of observations, a plurality ofmeasuring means responsive to a predetermined condition, totalizingmeans, and means successively actuating said totalizing means inproportion to the output in: dication of each of said measuring means ina sequence including a single indication taken from each and every oneof said measuring means.

6. In a system for averaging a plurality of observations of apredetermined condition, a plurality of sensing means responsive tovariations in the condition under measurement, metering means adapted toconvert the output of said sensing means into stimuli indicative of saidcondition, switching means successively connecting said sensing means tosaid metering means in a sequence including each 01' said sensing means,totalizing means driven by associated motor means, and means forcontrolling the operation of said motor means in response to saidstimuli.

7. In a system responsive to the average of a plurality of observations01' a predetermined con dition, a plurality of measuring meansresponsive to variations in said condition, means successively andadditively driven in response to the indications of said measuringmeans, a circuit controller normally in a first condition, actuatingmeans for placing said circuit controller in a second condition whensaid additively responsive means is driven past a predetermined point,means for retaining said circuit controller in said second condition,restoring means for releasing said retaining means when said additivelyresponsive means has not been driven past a predetermined point, anddisablingmeans preventing operation of said actuating and restoringmeans except after the actuation of saidv additively responsive means bya predetermined number of said measuring means.

8. In a system responsive to the average of a plurality of observationsof a predetermined condition, a plurality of measuring means responsiveto variations in said condition, means successively and additivelydriven in response to the indications of said measuring means, switchingmeans normally in a first position, relay means controlled by saidadditively responsive means for driving said switching means into asecond position, means for retaining said switching means in said secondposition, relay means controlled by said additively responsive meansadapted to release said retaining means, an electric energy sourceadapted to energize said relay means, and a normally open switchinterposed between said electric energy source and said relay meansperiodically closed after the summation of the indications of apredetermined number of said measuring means.

9. In a system responsive to the average of a plurality of observationsof a predetermined condition, .a plurality of measuring means responsiveto variations in said condition, control means successively connected toeach of said measuring means at predetermined time intervals, a summingdevice actuated by a driving motor, means initiating the operation ofsaid driving motor at times spaced by said predetermined time intervals,means responsive to said control means for interrupting the operation ofsaid motor, meansfor zercizing said summing device after the successiveconnection of a predetermined number of said measuring means to saidcontrol means, and circuit controlling means actuated by said summingdevice energized after the successive connection of a predeterminednumber of said measuring means prior to the actuation of said zeroizingmeans.

' 10. In a system responsive to a plurality of observations ofpredetermined conditions, a plurality of test stations adapted in afirst circuit to respond electrically to variations in a first conditionand in a second circuit to variations in a second condition, means forcyclically and sequentially linking said test stations to a meteringcircuit, means for connecting said first test station circuit to saidmetering circuit during a first fraction of the connection cycle andsaid second test station circuit to said metering circuit during theremaining fraction of said connection cycle, a continuously movingdevice bearing a first set of characters corresponding to said firstcondition and a second set of characters corresponding to said secondcondition, a first printer means adapted to cooperate with said firstset 01' characters under the control of the active test station duringsaid first fraction of said connection cycle, and a second printer meansadapted to cooperate with said second set of characters during theremaining fraction of said connection 0 ole.

ll. In a system responsive to a plurality of observations ofpredetermined conditions, a plurality of test stations adapted in afirst circuit to respond electrically to variations in a first conditionand in a second circuit to variations in a second condition, meanscyclically operable for sequentially linking said test stations to ametering circuit, means for connecting said first test station circuitto said metering circuit during a first fraction of the connection cycleand said second test station circuit to said metering circuit during theremaining fraction of said connection cycle, a first character bearingdevice provided with characters corresponding to said test stationsintermittently indexed in position synchronously with the operation ofsaid cyclically operable means, a continuously moving device bearing afirst set of characters corresponding to said first condition and asecond set of characters corresponding to said second condition, a thirdcharacter bearing device movable under the influence of timing means, afirst printer means adapted to cooperate with said first characterbearing device and one of said condition corresponding sets ofcharacters under the control of the active test station during saidfirst fraction of said connection cycle, and a second printer meansadapted to cooperate with said third character bearing device and theother of said condition corresponding sets of characters under thecontrol of said active test station during the remaining fraction ofsaid connection cycle.

12. In a system responsive to a plurality of observations of apredetermined condition, a plurality of measuring means responsive tosaid condition, selector means for sequentially connecting saidmeasuring means with metering apparatus, a source of motive power, meansfor initiating operation of said source of motive power substantially atthe connection of one of said measuring means to said meteringapparatus, and means controlled by said metering apparatus forinterrupting the operation of said source of motive power.

13. In a control system, means for additively combining a plurality ofmeasurement stimuli applied in time sequence, a first switching meansactuated by said additive combining means, normally restrained means forresetting said additive combining means to a reference position, asecand switching means connected with said first switching means andactuated after the application of each measurement stimulus, and meansfor releasing the normal restraint on said reset means after thecompletion of the actuation cycle of said second switching means.

14. In a control system, means for additively combining a plurality ofmeasurement stimuli applied in time sequence, a first switching meansactuated by said additive combining means, normally restrained means forresetting said additive combining means to a reference position, asecond switching means connected with said first switching means andactuated after the application of each measurement stimulus, electricalmeans for releasing the normal restraint on said reset means after thecompletion of the actuation cycle of said second switching means, and athird switching means connected with saidsecond switching means and saidelectrical release means periodically actuated after the application ofa predetermined number 01 said measurement stimuli.

accuse 15. In a control system, means for additively combining aplurality ofmeasurement stimuli, selector means sequentiallyindividually connecting stimulus producing means with a plurality ofcondition responsive devices, means sequentially applying said stimulito said combining means, means driving said selector means, a firstswitching means actuated by said combining means. normally restrainedmeans for resetting said combining means to a reference position, asecond switching means connected with said first switch-' ing means andactuated after the application of each measurement stimulus, electricalmeans for releasing the normal restraint on said reset means aftercompletion of the actuation cycle 0! said second switching means, and athird switch- 22 inc means actuated by said selector driving means afterthe application of a predetermined number of said measurement stimuli tosaid combining means connected with said second switching means and saidelectrical release means.

RUTGER B. COLT.

REFERENCES CITED The following references are of record in the m file ofthis patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,467,929.April 19, 1949.

RUTGER B. COLT It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows:

Column 6, line 74, for the word portion read portions; column 18, line15, claim 1, for deriving read responswe to;

and'that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Ofiice.

Signed and sealed this 4th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommzasioner of Patents.

ertificate of Correction Patent No. 2,467,929. April 19, 1949.

RUTGER B. COLT It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows:

Column 6, line 74, for the word portion read portions; column 18, line15, claim 1, for deriving read responsive to;

and'that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 4th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

